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Freezer Iced Up At The Back
A thick sheet of ice building up on the rear wall of the freezer, eating the space and eventually stopping the fridge cooling too.
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What's happening?
Ice on the back wall of a freezer is moisture that has got in and then frozen where the evaporator is coldest. In a frost-free appliance that should never accumulate, because a heater melts the frost off the evaporator periodically and the water runs away down a drain channel to a tray above the compressor, where it evaporates. So heavy icing in a frost-free freezer means one of three things: too much moist air is getting in, the defrost cycle is not working, or the drain is blocked and the meltwater is refreezing. In an older static or manual-defrost freezer, gradual icing is normal and it simply needs defrosting. The reason it matters is that on a fridge freezer the same iced evaporator eventually blocks the airflow that cools the fridge compartment.
What usually causes it?
- A door seal that has hardened, split or distorted, letting warm moist air in continuously
- A door left ajar, or a drawer or package stopping it closing fully
- A failed defrost heater or defrost thermostat, so frost is never cleared
- A blocked defrost drain channel, so meltwater refreezes instead of draining away
- Putting warm or uncovered food straight in, adding moisture each time
- A garage or outbuilding location outside the appliance's rated climate class
- A door alignment or hinge problem after the appliance was moved
- Frequent, prolonged door openings in a warm, humid kitchen
Is it dangerous?
Not dangerous, but destructive in a slow way. Ice forces the appliance to run longer for less effect, which costs money and shortens its life, and expanding ice can distort shelving, split the evaporator cover and damage the fan. The real hazard is in how people remove it: chipping at ice with a knife or a screwdriver punctures the evaporator, and once the sealed system is pierced the appliance is finished — the refrigerant in modern domestic units is commonly isobutane, which is flammable. Never attack freezer ice with a sharp tool.
Can I fix it myself?
Yes, most of this is homeowner work. Empty the freezer, switch it off and let it defrost fully with the door open and towels down — a bowl of hot water inside speeds it up, and so does a hairdryer used at a distance, kept away from standing water. While it is empty, find and clear the defrost drain hole at the base of the rear wall, which is very often the whole problem, and check where the water is supposed to go. Clean and dry the seal, then test it with a sheet of paper in the closed door: if it pulls out without drag, the seal has gone. Do not chip, scrape or lever the ice.
When should you call an appliance repair engineer?
Call an engineer when the ice returns within weeks of a full defrost with a good seal, which points at the defrost heater or thermostat rather than habits. Call also if the fridge compartment has started to warm up, if the fan is audibly catching on ice, if there is water pooling in the fridge or on the floor from a blocked drain you cannot clear, or if the door will not sit square after being moved or rehung.
What will the appliance repair engineer actually do?
- Defrost the appliance properly and inspect the evaporator and cover for ice damage
- Test the defrost heater and defrost thermostat for continuity and correct switching
- Check the defrost timer or the board's defrost control, and the drain path to the tray
- Clear or re-route a blocked drain channel and check the tray above the compressor
- Test the door seal and adjust hinges or alignment where the door is not closing square
- Replace the seal, heater or thermostat, then verify a full defrost cycle completes
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